Quenched spark gap



NQV. 19, 1940. w SCHQNFELD 2,222,268

' QUENCHED SPARK GAP Filed Nov; 50, 1938 2 Sheets-Sheet l KKKKKKKKKINVENTDR WILHEL s ONFELD v BY I ATTORNEY QUENCHED SPARK GAP Filed Nov.30, 1938 2 Sheets-Sheet 2 INVENTOR Mum/4122, 510 BY ATTQRNEY PatentedNov. 19, 1940 PATENT OFFICE QUENCHED SPARK GAP Wilhelm Schiinfeld,Berlin, Germany, assignor to Telefunken Gesellschaft fiir DrahtloseTelegraphic m. b. 11., Berlin, Germany, a corporation of GermanyApplication November 30, 1938, Serial No. 243,219 In Germany November13, 1937 2 Claims.

An object of this invention is to provide a quenched spark gappossessing a high quenching effect with very low self-capacitance andvery low self-inductance.

The present invention is related to a new and novel series quenchedspark gap which offers substantial advantages over similar arrangementsknown in the prior art. Fundamentally speaking, it is known to userotating spark gaps for the generation of high frequency currents. Forthe production of short waves, in order that the ensuing oscillationsmay be of low damping and cooling of the discharge gaps, theinterelectrode distances must be extremely small. Most favorable aredistances of, say, an order of a few hundredths of 1 mm. Rotating theelectrodes in reference to one another in the revolving series sparkgaps known in the art, it will be found very difficult to observe ormaintain such small distances or gaps, and the consequence is that evenslight alterations will cause serious variations in operation. Anotherfact is that the spark gaps known in the art, of the rotary type, inhereconsiderable self-capacitance which represents a substantial shunt whereultra-short waves are dealt with.

According to the invention a quenched spark gap is designed in such away that a series or row of juxtaposed series spark gaps is periodicallypassed between two stationary end or terminating electrodes upon whichthe discharge potential is impressed.

An exemplified embodiment of a spark gap as here disclosed consists ofarotatable hollow cylinder upon the shell or circumference of which theseries spark gaps are disposed in the form of several adjacent rowscovering the circumference of the cylinder parallel to the axis ofrotation of the hollow cylinder, in such a way that upon rotation of thecylinder the various series of spark gaps are positioned between the twofixed electrodes at the beginning and the end.

The invention shall nowbe explained more fully by reference to theappended drawings which show this exemplified embodiment. Fig. 1 is alongitudinal section of the object of the invention; Fig. 2 is across-section. W denotes a steel shaft or spindle journaled in the ballbearings L, said shaft W being rotated by a motor M. Thesaid shaft Wsupports a hollow cylinder H made of insulation material upon thecircumference of which, being separated from one another by a thin layerof asbestos, are secured the copper radiator or cooling elements K.Welded onto the latter are the electrodes E, the

latter preferably being made of tungsten or electrolytic iron. El and E2represent the two electrodes mounted at the beginning and at the endwhich are welded on the radiator or chilling bodies KI and K2,respectively. These fixed cooling elements may be adjusted in distancerelative to the spark gap by screw-threads GI and G2, and they arecooled by the aid of vanes FI and F2 attached to the shaft. As can beseen from the cross-sectional view Fig. 2 of the revolving part of theassembly, 24 series spark gaps are arranged on the circumference of thehollow cylinder in the particular exemplified em bodiment here shown,which, upon rotation, are sequentially placed in a position between theelectrodes El and E2. The cooling of the spark gap is insured byblasting a current of air against the same from below.

Now, the operation of the spark gap is as follows:

By rotation of the central electrode, ever freshly cooled and deionizedgaseous paths or gaps are shifted into the spark path. This path or gapis fixed by the stationary outer electrodes El and E2 and fixed anddefined by the line connecting the first and the last electrodes. In theinstance here mentioned comprising 24 spark gaps around thecircumference of the revolving hollow cylinder, as will thus be seen, acold deionized gaseous path will enter the spark gap twenty-four timesfor each revolution. Thus, if the hollow cylinder requires for arevolution, say, one second, this means that the gas path of a series ofconsecutively disposed electrodes stays just one-tWenty-fourth of onesecond in the spark path. In other words, the copper radiator elements Khaveof a second time to give off such heat as may have been generated.In the ten-unit spark gap as represented in the exemplified embodiment,the resultant thermal load of the spark gap amounts to only 400 watts.This load, in the case of a stationary spark gap, would have to bedivided between twenty electrodes, whence the heat dissipated and to becarried away per electrode would amount to twenty watts. But in therotary spark gap according to the present embodiment, the 400 watts aredivided among a twenty-four times greater number of electrodes, whence aload of less than two watts. Owing to such low heat load and to themovement of the electrodes, the tendency to form craters is avoided,combined with very effective cooling and deionization. Because of suchlow heat load, moreover, the radiator elements can be made comparativelysmall in size. And this means very low self-capacitance of the entireassembly with the result that the shunt residing in this capacity andwhich for ultra-short waves is conducive to marked losses, is greatlyreduced. The self-capacitance of the spark gap shown in the exemplifiedembodiment amounts, for instance, to only around 2 centimeters.

The abbreviation of the current path due to the compact and crowdedarrangement of the electrodes, as contrasted with the conventionalstationary spark gap, amounts to about eighty percent. As a result, theself-induction of the spark gap which constitutes part of the inductanceof the oscillatory circuit is diminished considerably. The condenser ofthe oscillatory circuit, for the generation of waves of the same length,may therefore be made larger, and this means an appreciable raise inpower.

Owing to the efficient cooling of the spark gap, it is possible to useextremely high spark frequencies, say, up to 10 per second, without thespark becoming inductive as a result of inadequate or imperfectde-ionization. Also, this fact raises the oscillatory power orperformance of the arrangement considerably.

By mounting additional stationary electrodes at the beginning and at theend, further spark paths may be obtained which may be used either forimpulsing other oscillatory circuits or as spare gaps. To insure equallygood cooling conditions in this case, the number of electrodesdistributed over the periphery and the speed of rotation must beincreased correspondingly.

The invention is not restricted to the exemplified embodimentillustrated in the drawings,

but a great many modifications are conceivable which fall inside thescope and spirit of the invention.

What is claimed is:

1. A quenched spark gap comprising a rotatable shaft, a ventilation vanemounted on said shaft for cooling said spark gap, an insulatingcylindrical member secured to said shaft, a plurality of metallic discsmounted on said insulating cylindrical member, a plurality of metallicelectrode members secured to both surfaces of each disc and forming arow of juxtaposed series spark gaps, a pair of fixed terminalelectrodes, said discs arranged in a row periodically between said fixedelectrodes so that electrical discharge applied to one of said fixedterminal electrodes passes through said series spark gaps and isdischarged at an opposite fixed terminal electrode.

2. A quenched spark gap comprising a rotatable device, a rotatable shaftsecured to said rotatable device, a ventilation vane mounted on each endof said shaft for cooling said said spark gap, an insulating cylindricalmember secured to said shaft, a plurality of metallic discs mounted onsaid insulating cylindrical member, a plurality of metallic electrodemembers secured to both surfaces of each disc and forming a row ofjuxtaposed series spark gaps, a pair of fixed terminal electrodeslocated adjacent said ventilation vanes, said discs arranged in a rowperiodically between said fixed electrodes so that electrical dischargeapplied to one of said fixed terminal electrodes passes through saidseries spark gaps and is discharged at an opposite fixed terminalelectrode.

WILHELM SCHCNFELD.

